1. Cyril Stanley Smith: Grain Shapes and Other Metallurgical Applications of Topology. Paper in Metal Interfaces (1952) pp. 65–113. Cleveland. ASM.
2. ASTM Classification of Grain Size in Steels, ASTM (a) Tentative Standard E-19-39T. (b) Preparation of Micrographs of Metals and Alloys (Including Grain Size Standards for Non-Ferrous Metals), ASTM Standard E2-44T.
3. E. Scheil: Statistical Investigations of the Structures of Alloys. Ztsch. Metallkunde (1935) 27, pp. 199–208; (1936) 28, pp. 340-343.
4. W. A. Johnson: Estimation of Spatial Grain Size. Metal Progress (1946) 49, (1), pp. 89–92.
5. J. B. Rutherford, R. H. Aborn, and E. C. Bain: Relation of Grain Area on a Plane Section and the Grain Size of a Metal. Metals and Alloys (1937) 8, pp. 345–348; ASM Metals Handbook (1948) p. 405.